Backport useMongoClient option

From Automattic#5355

lib/connection.js

@@ -11,6 +11,7 @@ var STATES = require('./connectionstate');
 var MongooseError = require('./error');
 var muri = require('muri');
 var PromiseProvider = require('./promise_provider');
+var mongodb = require('mongodb');
 
 /*!
  * Protocol prefix regexp.
@@ -578,6 +579,52 @@ Connection.prototype.onOpen = function(callback) {
   }
 };
 
+/**
+ * Opens the connection with a URI using `MongoClient.connect()`.
+ *
+ * @param {String} uri The URI to connect with.
+ * @param {Object} [options] Passed on to http://mongodb.github.io/node-mongodb-native/2.2/api/MongoClient.html#connect
+ * @param {Function} [callback]
+ * @returns {Connection} this
+ * @api private
+ */
+
+Connection.prototype.openUri = function(uri, options, callback) {
+  this.readyState = STATES.connecting;
+  this._closeCalled = false;
+
+  if (typeof options === 'function') {
+    callback = options;
+    options = null;
+  }
+
+  var Promise = PromiseProvider.get();
+  var _this = this;
+
+  if (options && options.useMongoClient) {
+    options = utils.clone(options, { retainKeyOrder: true });
+    delete options.useMongoClient;
+  }
+
+  return new Promise.ES6(function(resolve, reject) {
+    mongodb.MongoClient.connect(uri, options, function(error, db) {
+      if (error) {
+        _this.readyState = STATES.disconnected;
+        if (_this.listeners('error').length) {
+          _this.emit('error', error);
+        }
+        return reject(error);
+      }
+      _this.db = db;
+      _this.readyState = STATES.connected;
+
+      callback && callback();
+      resolve(_this);
+      _this.emit('open');
+    });
+  });
+};
+
 /**
  * Closes the connection
  *

lib/index.js

@@ -170,7 +170,7 @@ var checkReplicaSetInUri = function(uri) {
  * @param {Boolean} [options.config.autoIndex] set to false to disable automatic index creation for all models associated with this connection.
  * @see Connection#open #connection_Connection-open
  * @see Connection#openSet #connection_Connection-openSet
- * @return {Connection} the created Connection object
+ * @return {Connection|Promise} the created Connection object, or promise that resolves to the connection if `useMongoClient` option specified.
  * @api public
  */
 
@@ -179,6 +179,11 @@ Mongoose.prototype.createConnection = function(uri, options) {
   this.connections.push(conn);
 
   var rsOption = options && (options.replset || options.replSet);
+
+  if (options && options.useMongoClient) {
+    return conn.openUri(uri, options);
+  }
+
   if (arguments.length) {
     if (rgxReplSet.test(arguments[0]) || checkReplicaSetInUri(arguments[0])) {
       conn.openSet.apply(conn, arguments);
@@ -227,6 +232,7 @@ Mongoose.prototype.createConnection.$hasSideEffects = true;
  *
  * @param {String} uri(s)
  * @param {Object} [options]
+ * @param {Boolean} [options.useMongoClient] false by default, set to true to use new mongoose connection logic
  * @param {Function} [callback]
  * @see Mongoose#createConnection #index_Mongoose-createConnection
  * @api public
@@ -235,6 +241,13 @@ Mongoose.prototype.createConnection.$hasSideEffects = true;
 
 Mongoose.prototype.connect = function() {
   var conn = this.connection;
+
+  if ((arguments.length === 2 || arguments.length === 3) &&
+      typeof arguments[0] === 'string' &&
+      typeof arguments[1] === 'object' &&
+      arguments[1].useMongoClient === true) {
+    return conn.openUri(arguments[0], arguments[1], arguments[2]);
+  }
   if (rgxReplSet.test(arguments[0]) || checkReplicaSetInUri(arguments[0])) {
     return new MongooseThenable(this, conn.openSet.apply(conn, arguments));
   }

package.json

@@ -72,7 +72,8 @@
     "install-browser": "npm install `node format_deps.js`",
     "test": "mocha test/*.test.js test/**/*.test.js",
     "posttest": "eslint . --quiet",
-    "test-cov": "istanbul cover --report text --report html _mocha test/*.test.js"
+    "test-cov": "istanbul cover --report text --report html _mocha test/*.test.js",
+    "mocha": "mocha"
   },
   "main": "./index.js",
   "engines": {

test/connection.test.js

@@ -14,6 +14,30 @@ var muri = require('muri');
  */
 
 describe('connections:', function() {
+  describe('useMongoClient/openUri (gh-5304)', function() {
+    it('with mongoose.connect()', function(done) {
+      var promise = mongoose.connect('mongodb://localhost:27017/mongoosetest', { useMongoClient: true });
+      assert.equal(promise.constructor.name, 'Promise');
+
+      promise.then(function(conn) {
+        assert.equal(conn.constructor.name, 'NativeConnection');
+
+        return mongoose.disconnect().then(() => done());
+      }).catch(done);
+    });
+
+    it('with mongoose.createConnection()', function(done) {
+      var promise = mongoose.createConnection('mongodb://localhost:27017/mongoosetest', { useMongoClient: true });
+      assert.equal(promise.constructor.name, 'Promise');
+
+      promise.then(function(conn) {
+        assert.equal(conn.constructor.name, 'NativeConnection');
+
+        return mongoose.disconnect().then(() => done());
+      }).catch(done);
+    });
+  });
+
   it('should allow closing a closed connection', function(done) {
     var db = mongoose.createConnection();